[Chicken-users] about egg/pty

[Chaos Eternal]

hi all
by browsing the code of pty egg (http://wiki.call-cc.org/eggref/4/pty)

in source code 
http://code.call-cc.org/svn/chicken-eggs/release/4/pty/trunk/pty.scm
the procedure

 raw-open-pty

uses a magic number 1024 , which used to pack master fd and slave fd
into one integer to return.

but why 1024 and what happens when the slave fd is greater than 1024?

just curious.